Groundwater pollution assessment using statistical and index based methods in the Wassa area Ghana and its implications for human health
Millicent Obeng Addai
Abstract
Groundwater extraction in southern Ghana has gained importance because various environmental conditions, including Artisanal Small-scale Gold Mining (ASGM) operations and agricultural practices, along with urban development, have damaged surface water reservoirs. This study statistically and index-wise assessed the quality of 150 groundwater samples from the Wassa area using multivariate techniques and contamination indices, including the Pollution Index of Groundwater (PIG), Fluoride Pollution Index (FPI), and Nitrate Pollution Index (NPI). The borehole water analysis included physicochemical parameters that underwent three methods: Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and correlation assessments to map the pollution origins and geochemical regulation. The findings regarding pH measurement demonstrated an average value of 6.94 (range: 5.73–8.45), producing mildly acidic water conditions that match WHO guidelines (6.5–8.5). Total dissolved solids (TDS) averaged 155.97 mg/L (range: 6.51–382 mg/L), and total hardness (TH) averaged 60.56 mg/L, with 62.96% of samples exceeding the 100 mg/L desirable limit. All examined groundwater samples met the WHO standards based on analytical tests of TDS, EC, alkalinity, Na + , Ca 2+ , Mg 2+ and Cl − , SO 4 2− , though 3.7% of samples showed fluoride levels above 1.0 mg/L and 1.98% exhibited significant nitrate contamination. PIG values indicated generally low to moderate contamination, with a mean of 0.18 (< 1 for 100% of samples), while the mean FPI of 1.67 classified most samples as low fluoride risk. The health risk assessment performed using USEPA guidelines showed that children experienced the highest non-carcinogenic risks, with 24.75% of samples exceeding THI = 1, compared to 7.92% in women and 4.95% in men. Research findings confirmed the roles of natural factors and human activities in degrading groundwater quality, therefore demanding specific monitoring and policy measures to prevent long-term health problems in mining areas.